Automatic conveyers are used industrially, commercially, and in service functions such as the post office. They are controlled by electro-mechanical servo-systems to regulate flow, speed, storage, switching, stopping, starting, etc. These devices have means for sensing and determining the presence or absence of items on the conveyer, such as mail trays in a post office which are used herein as exemplary of items being carried by conveyers.
The devices of the prior art which provide regulation of conveyers are complicated in design and construction, expensive to manufacture, install and relocate, difficult and complicated to mount and remount at other locations, and involve additional work in attaching and adjusting the switches which they actuate.
Conveyers may be hundreds and thousands of feet in length and require many item sensing and determining devices along their length so that the other functions of the conveyer will be properly coordinated with the ambient load conditions of the conveyer.
Thus the prior art devices leave much to be desired as far as initial installation is concerned and also in the relocating of the devices to suit changed conditions as the conveyer control systems must be changed when load conditions change, when new load handling equipment is added, and when space, storage, work, aisle, loading and unloading conditions change.
The prior art sensing devices and the switches which they actuate thus should be improved so that they are more efficient initially and during their worklife.